Seventeen Castaic residents sent a letter of notice to the William S. Hart Union High School District and the developers of the Castaic High School site, claiming runoff water from the school puts homes in Romero Canyon at “imminent risk of harm.”

Attorney Gregory Goodheart wrote a 20-page letter to 11 groups including C.A. Rasmussen, Spirit Holdings, the school district and three county agencies that said flood damage would occur if the developers did not take precautions.

“The homeowners wish to alert all named entities above of the real and imminent danger of damage to property and life as a result of flood waters caused as a result of the building of the Castaic High School,” Goodheart wrote.

In a statement released to The Signal Friday, the William S. Hart Unified School District said grading for the school is complete, the overall construction of the site is about 40 percent complete and it had received approvals for construction from eight different agencies including the U.S. Army Corps. of Engineers, the California Geologic Survey and Los Angeles County Department of Public Works.

“These approvals took many years to obtain and involved a multitude of consultants of various disciplines related to this type of development. Environmental Impact Studies, environmental impact reports, jurisdictional wetlands delineations, topography surveys, geologic investigations, and hydrology studies were all prepared, reviewed and approved. Third-party monitors of various disciplines have ensured the strict adherence to the permits and approvals issued to the district for this project,” the statement said.

Randy Wrage, the manager of the construction project, said some residents have been against the building of the high school for years.

“They just don’t want a high school there,” he said Thursday. “It’s a neighbor dispute.”

A Los Angeles County Department of Public Works spokesman said the agency was aware of the letter.

Goodheart said last year’s rainy season instigated the residents’ concerns.

“These homeowners became aware of the flood water problem with last winter’s moderate rains, which produced run-off in excess of what any of the residents had witnessed in 20 years,” he wrote. “There had been periods of much harder and more prolonged rains in the past which did not produce anything remotely near the run-off which occurred last winter with the grading and construction of the school site.”

Goodheart said the school site, which spans about 198 acres, cleared land that was undeveloped and changed the makeup of the soil.

“In order to construct the school site, literally millions of yards of alluvial soil was removed and/or compacted significantly, greatly reducing the natural soil absorption and percolation of rainwater into the earth,” he wrote. “In turn, this change drastically increased the amount of runoff from the site into the Romero Canyon community below.”

The school district’s statement said the drainage system was approved with conditions in Romero Canyon before and after the school is fully built in mind.

“The approved drainage system was designed in consideration of both the pre-existing conditions within Romero Canyon and the fully improved high school site, yet to be completed. Romero Canyon is a County of Los Angeles adopted floodway. Per the floodway map, during a ‘Capital Storm’ (50-year event) the storm flow is approximately 1,700 to 2,000 cubic feet per second. The consultant for the school district was required to perform extensive hydrologic and hydraulic analysis under multiple storm event scenarios to show that there was no change in storm flow characteristics leaving the school site based on pre- and post-development conditions,” the statement said.

The statement added: “In summary, the development of the district property is designed to not have an impact on the current conditions within the canyon. There will still be significant flows of water and/or debris in low-lying areas during major storm events as a result of natural drainage tendencies, the lack of an improved downstream drainage system, and the reality that Romero Canyon has a stream running through it.”

Goodheart said homeowners are concerned runoff from the school would overflow concrete V-ditches at the edge of the school property and adjacent reservoirs.

“Once again, during last winter’s moderate rains, evidence of the inadequate nature of the reservoirs/dams became apparent,” he wrote. “The dams quickly filled to capacity, with moderate rainfall, and expelled great amounts of water into the spillway which dumped into a streambed which could not begin to hold the water forced into it.”

Goodheart’s letter showed photos of damage in Romero Canyon last year that included a partially submerged vehicle, muddy roads and eroded drainage. Romero Canyon Road is a private road and is primarily a dirt road, though there is a portion that is paved.

“Of great concern to the residents of Romero Canyon is that during a heavy rain the water going into the reservoir will be more than the spillway can expel. At that point the excess water will overtake the earth dam and cut through and within minutes the entire dam will fail,” he wrote. “If such a breach does occur there is no doubt that there is a significant and real and present danger to property and life below the dam.”